Barrels are widely used in several engineering applications and mechanical systems. One such mechanical system, which employs a barrel, is a twin-screw extruder. In a typical twin-screw extruder, the barrel has a central bore in a shape of two horizontally intersecting circles. The barrel houses a pair of extruder screw shafts with extruder screw elements mounted on each of extruder screw shafts.
Each of the pair of extruder screw shafts, having the extruder screw elements mounted on the screw shafts rotates to process the work material. The motion of the screw shafts and unequal loading of different barrel sections may cause jerks and random forces may lead to misalignment of barrel sections. Hence, it becomes necessary that centers of the barrel sections should match with those of the twin screws during the rotation of the screw shafts for smooth extrusion.
Further, various processes like conveying, kneading, mixing, devolatizing etc occur at different barrel sections at different temperatures. As a result, the temperature distribution along the barrel is non-uniform. Hence, the barrel sections undergo differential thermal expansion. Due to this differential thermal expansion, misalignment of barrel sections may take place. Hence, it is desirable to have a barrel assembly, which ensures alignment of different barrel sections notwithstanding the adverse temperature differences.
Various systems have been proposed to maintain the alignment of barrel section. However, these systems were only partially successful in addressing the misalignment problems. In the conventional mechanical systems, bolts are used to join the barrel sections. Although bolt joints solve the problem of misalignment due to uneven forces to a certain extent, such joints do not allow for thermal expansion of barrel sections. This constrained thermal expansion may lead to deformation of barrel sections resulting in misalignment of the barrel sections.
In another conventional system, long bars are passed through bores in the flanges of barrel sections. However, again this arrangement has problems in terms of constrained thermal expansion. This arrangement may also lead to residual stresses in the material of the barrel sections. Hence, there is a need for a barrel assembly in which the alignment of barrel sections is ensured under all thermal conditions. It is also desirable to have a barrel assembly in which the alignment of the barrel sections withstands unequal force distribution. It is further desirable to have a barrel assembly in which the alignment is ensured without formation of stresses.